Packaged radiation sensitive coated workpiece process for making and method of storing same

ABSTRACT

The present invention includes a packaged coated workpiece. The packaged coated workpiece has: (1) a workpiece coated with a resist film sensitive to optical radiation, particulates or chemical contaminants; (2) an inner barrier sealed to enclose the coated workpiece and optionally a first getter agent, to produce a sealed first enclosure; and (3) an outer barrier sealed to enclose the sealed first enclosure and optionally a second getter agent, provided that the packaged coated workpiece has at least one getter agent, to produce a packaged coated workpiece suitable for storage for a period of at least one week without substantial loss of sensitvity, resolution or performance. The present invention also includes a process for preparing a packaged coated workpiece and a method of increasing the storage time of a coated workpiece to at least one week without substantial loss of sensitivity, resolution or performance.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a coated workpiece packaged in a sealedenclosure comprising one or more barriers and getter agents in anenclosure substantially free of chemical contaminants for storagewithout loss of sensitvity, resolution or process latitude. Moreparticularly, the present invention relates to a package for storingenvironmentally sensitive resist-coated mask blanks.

2. Description of the Related Art

Chemically Amplified Resists (CAR) are extremely sensitive tocontaminants. In microelectronic device manufacturing, ChemicallyAmplified Resists are generally manufactured and used on site incontrolled environments and tool sets. They are not packed for storage.In mask blank writing, the mask blank manufacturer coats the blanks witha Chemically Amplified Resist, generally in a mask shop, and ships themto a location where they can be exposed and subsequently processed intoa mask. In such cases, packaging is of great importance.

One of the problems associated with the manufacture and shipping ofresist-coated mask blanks has been the variability in the performance ofthe resist-coated mask blanks resulting from variable degree ofcontamination. Because the presence of a defect in the resist-coatedmask blanks can not be detected by practical methods at an early stage,such defects do not surface until at a very advanced stage of use, i.e.,after many hours of imaging and development work when degradation of theproperties of the resist-coated mask blanks become obvious.

Proper storage of coated films of photosensitve materials is a commonproblem associated with humidity, heat, and solvent absorption. Theseeffects are described, for example, in: (1) U.S. Pat. No. 6,120,983; (2)an article by H. Ito and M. Sherwood, J. Photopolymer Science and Tech.,12, 625-636 (1999), which discloses an investigation of a DUV resist byNo including aspects of residual casting solvent and PAG decompositionin a film and storage effects; and (3) G. Czech, et al., MicroelectronicEngineering, 23, 331-5 (1994), which describes the influence of DMF onprofiles of chemically amplified resists. In addition, the chemicallyamplified resists are susceptible to absorption of amines and moisture,as described in an article entitled “Airborne Contaminants andChemically Amplified Resist Stability” by W. Hinsberg, S. MacDonald, N.Clecak, C. Snyder and H. Ito, SPIE Proceed., 1925, 43-53 (1993). U.S.Pat. Nos. 5,985,524; 5,962,184; 5,861,231; 5,712,078; 5,585,220;5,296,332 and 4491628 describe chemically amplified resist (CAR) basedon acid catalyzed removal of acid sensitive resists containing acidsensitive functional groups, such as, t-butylesters, carbonates, acetalsor ketals. Base sensitive resists are also known. Both type resists havebeen developed over the last twenty years as fast resists of highresolution for photolithography with doses of <50 mJ/cm² and forelectron beams in the range of <50 μC/cm².

Fast and high resoltuion resists that are exposable by electron beams orlaser beams at all wavelengths are also vital for next generationproduction of photomask blanks (see “Positive Chemically AmplifiedResist for Next Generation Photomask Fabrication” by T. Segaw et al.,SPIE Proceed., 3236, 82-93 (1999)). In this process, precoated plates ofresist on chrome covered quartz are written by a laser or electron beampattern generator. Precoated plates are generally received from a blankmanufacturer.

Because the films of resist are very thin, i.e., <400 nm thick, a coatedsix inch square plate has only about 10 mg of resist which would besusceptible to microgram levels of absorbed acid, which may subsequentlycatalyze the deprotection reactions of the amplified resists. Thus forlong term storage of the CAR resists, the storage environment should befree of even minute quantities of acids, particularly acids having apK_(a)<6, bases having a pK_(b)<6, as well as solvents and moisture.Ambient air contains moisture and can also contain acid precursors, suchas, sulfur dioxide (SO₂) and nitrogen oxide (NO₂), which are commoncontaminants in the environment occuring generally at ppm levels. Forcontamination caused by acid precursors, see J. Lynch, C. VanBowersoxand J. Grimm, Environmental Science and Technology, 34, 940-9 (2000).

Prior art attempts to preserve chemically amplified resist (CAR) haveinvolved providing a topcoat of polyacrylic acid, as described in anarticle entitled “Effect of Gaseous Peremeability of Overcoat Layer onKrF Chemically Amplified Positive Resists” by S. Kishimura, J. Sakai, K.Tsujita and Y. Matsui, J. Vac. Sci and Tech., B14, 4234-8 (1996), orfiltering the contacting environment to remove ammonia and amines, asdescribed in an article entitled “Development of Ammonia AbsorptionFilter and Its application in LSI Manufacturing Environment” by A.Saiki, et al., J. Photopolymer Science and Tech., 8, 599-606 (1995). Insome cases, such topcoats have caused deteriorated performance (processscumming) and/or have introduced coating defects to the resist film, asdescribed in the previously cited S.Kishimura, J. Sakai, K. Tsujita andY. Matsui, J. Vac. Sci and Tech., B14, 4234-8 (1996). Filtration of theprocess air has been used to prevent “T-top” scumming during thepost-expose bake, as described in previously cited W. Hinsberg, S.MacDonald, N. Clecak, C. Snyder and H. Ito, SPIE Proceed., 1925, 43-53(1993) and A. Saiki, et al., J. Photopolymer Science and Tech., 8,599-606 (1995). However, this approach has not been used with acidicvapors or under long term storage conditions.

U.S. Pat. No. 6,120,860 describes a package to store reactive liquidorganic amines inside a bag. The package uses aluminzed nylon coatedwith polyvinylidene chloride. This patent does not make any reference tostorage of a workpiece coated with a resist film that is sensitive tooptical radiation, particulates or chemical contaminants, includingoutgassing acids, vapors and moisture. No getter agents are included inthis package.

Acid catlyzed deprotection of radiation sensitive chemically amplifiedpolyhydroxystyrene ketal resists used for mask-making and their storageis described in U.S. Pat. Nos. 6,043,003 and 6,037,097 and W. Huang, etal., “A CA Resist with High Sensitivity and sub 100 nm Resolution forAdvanced Mask Making,” Proceedings of SPIE, Vol. 4066, pages 150-159(2000). Attempts to preserve plates by packaging the coated plates in asingle layer polymer package, i.e., a single plastic bag, are describedin U.S. Pat. Nos. 6,043,003 and 6,037,097. However, this method is notadequately effective. For example, it is not effective aginst permeationof acidic or basic organic or inorganic vapors or potential outgassingacids, vapors and moisture from the packaging materials themselves, fromthe resist coated mask blanks or from the carrier or holder of theresist coated mask blanks.

None of the above references describe storage of environmentallysensitive resist-coated mask blanks without loss of sensitvity,resolution or process latitude in an enclosure substantially free ofchemical contaminants. None of the above references substantiallyaddresses the problem of variability in the performance of theresist-coated mask blanks resulting from variable degree ofcontamination. Because the presence of a defect in the resist-coatedmask blanks can not be detected by practical methods at an early stage,such a defect does not surface until at a very advanced stage of use,i.e., after many hours of imaging and development work when degradationof the properties become observable. None of the above references has asolution to the problem of variability in the performance of theresist-coated mask blanks or suggests a method of producing reprodicibleperformance attributes. Thus, there is a great need in industry formeans for reproducibly storing such coated films of photosensitvematerials without loss of sensitvity, resolution, process latitude andperformance.

It is highly desirable that plates coated with photosensitve materialsshould last at least three months and the resist should not change indose to print or in linewidth more than about 5%. Furthermore, since thechemically amplified resist (CAR) films would be particularity sensitiveto moisture and acid precursors, such as, SO₂ and NO₂, the physical orchemical removal of the vapors inside the package to store photomaskblanks would be highly desirable for protection against infiltration ofreactive vapors and outgassing contaminants.

Accordingly, it is the object of this invention to provide a packagedmaterial, such as a coated chemically amplified or non-chemicallyamplified resist plate, a process for preparing such a packaged materialand a method of storing such a material inside a package for a period ofat least three months to preserve the sensitvity, resolution andperformance thereof after such a storage.

SUMMARY OF THE INVENTION

The present invention includes a packaged coated workpiece comprising:(1) a workpiece coated with a resist film sensitive to opticalradiation, particulates or chemical contaminants; (2) a sealed enclosurecomprising one or more barriers for isolating the coated workpiece froman outside environment; and (3) one or more getter agents for producingan enclosure substantially free of chemical contaminants; wherein thepackaged resist coated workpiece is suitable for storage for a period ofat least one week without substantial loss of sensitvity, resolution orprocess latitude.

The present invention also includes a packaged coated workpiececomprising: (1) a workpiece coated with a resist film sensitive tooptical radiation, particulates or chemical contaminants; (2) a sealedenclosure comprising an inner barrier and outer barrier for isolatingthe coated workpiece from an outside environment; and (3) at least onegetter agent enclosed within the inner barrier and/or the outer barrierfor producing an enclosure substantially free of chemical contaminants.The packaged coated workpiece is suitable for storage for a period of atleast three months without substantial loss of sensitvity, resolution orprocess latitude.

The present invention further includes a packaged coated workpiececomprising: (1) a workpiece coated with a resist film sensitive tooptical radiation, particulates or chemical contaminants; (2) an innerbarrier sealed to enclose the coated workpiece and optionally a firstgetter agent, to produce a sealed first enclosure; and (3) an outerbarrier sealed to enclose the sealed first enclosure and optionally asecond getter agent, provided that the packaged coated workpiece has atleast one getter agent, to produce a packaged coated workpiece. Thecoated workpiece is suitable for storage for a period of at least oneweek without substantial loss of sensitvity, resolution or performance.

The present invention still further includes a process for preparing apackaged coated workpiece suitable for storage for a period of at leastone week without substantial loss of sensitvity, resolution orperformance. The process comprises the step of sealing a coatedworkpiece and a getter agent in a barrier to enclose the coatedworkpiece and the getter agent to produce the packaged coated workpiece.In another embodiment, the process comprises the steps of: (a) sealing acoated workpiece and optionally a first getter agent in an inner barrierto enclose the coated workpiece and the optional first getter agent toproduce a sealed first enclosure; and (b) sealing the sealed firstenclosure and optionally a second getter agent in an outer barrier toenclose the sealed first enclosure and the second optional getter agentto produce the packaged coated workpiece, provided that the packagedcoated workpiece has at least one getter agent.

The present invention additionally includes a method of increasing thestorage time of a coated workpiece to at least one week withoutsubstantial loss of sensitvity, resolution or performance. The methodcomprises packaging a coated workpiece by a process comprising the stepof sealing a coated workpiece and a getter agent in a barrier to enclosethe coated workpiece and the getter agent to produce the packaged coatedworkpiece. In another embodiment, the method comprises packaging acoated workpiece by a process comprising: (a) sealing a coated workpieceand optionally a first getter agent in an inner barrier to enclose thecoated workpiece and the optional first getter agent to produce a sealedfirst enclosure; and (2) sealing the sealed first enclosure andoptionally a second getter agent in an outer barrier to enclose thesealed first enclosure and the optional second getter agent to producethe packaged coated workpiece, provided that the packaged coatedworkpiece has at least one getter agent.

Using a combination of barrier materials and getter materials, thepresent invention provides a package system for storing a coatedworkpiece, such as a chemically amplified or non-chemically amplifiedresist plate, in a substantially dust free and chemically inertenvironment, for a period of at least one week without substantial lossof sensitvity, resolution and performance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a packaged coated workpiece in a sealedenclosure. The sealed enclosure comprises a single barrier and containsone or more getter agents.

FIG. 2 is a schematic of a packaged coated workpiece in a two barriersealed enclosure.

FIG. 3 is a plot of film loss versus wafer aging time for aging ofKRS-XE wafers at different temperatures and humidities.

FIGS. 4a, 4 b, 4 c and 4 d are Scanning Electron Micrographs (SEM) ofKRS-XE resist coated wafers resolved to 100 nm equal lines and spaces.

FIGS. 5a, 5 b, 5 c and 5 d are Scanning Electron Micrographs (SEM) ofKRS-XE resist coated wafers resolved to 75 nm equal lines and spaces.

DETAILED DESCRIPTION OF THE INVENTION

It has been discovered that a packaging structure having a singlebarrier, preferably two barriers, such as an inner and an outer barrier,sealed to enclose a getter agent, such as, a physical or chemical getteragent for moisture, acids and bases, provides superior preservation ofresist coated blanks.

In one embodiment, the present invention includes a coated workpiece anda getter agent enclosed in a single barrier.

The coated workpiece typically is a plate coated with a resist film,which can be a chemically amplified resist or a non-chemically amplifiedresist. Preferably, the coated workpiece is a resist-coated mask blank,such as, a resist-coated chrome film on a quartz blank.

Preferably, the coated workpiece is a substrate suitable formicroelectronic device fabrication or is a substrate suitable forfabrication of a mask, such as, an electron beam mask, x-ray mask,particle beam mask, excited state atom beam mask, ion beam mask or aphoto mask.

In another embodiment, the present invention includes a coated workpieceand a getter agent enclosed in a sealed inner barrier producing a firstsealed enclosure. The first enclosure and a second getter agent arefurther sealed in an outer barrier to produce the packaged coatedworkpiece according to this embodiment.

The packaged coated workpiece can further have a sealed intermediateenclosure between the inner barrier and the outer barrier, i.e., anintermediate barrier sealed to enclose the sealed first enclosure andoptionally an intermediate getter agent. The packaged coated workpiececan still further have additional intermediate barriers.

The packaged coated workpiece is suitable for storage for a period of atleast one week, preferably for a period of at least three months withoutsubstantial loss of sensitvity, resolution or performance.

The outer barrier provides a high barrier layer to infiltration ofacidic, basic vapors and moisture. The outer barrier encloses one ormore getters packaged in a microporous material to eliminatecontamination by particulates. The microporous material typically is ananoporous membrane prepared from, for example, a fluorinatedhydrocarbon material. Preferably, the fluorinated hydrocarbon materialis a fluorocarbon, vinylidene fluoride homopolymer, vinylidene fluoridecopolymer, Goretex™, Teflon™ or a combination thereof.

The inner barrier contains the coated workpiece, which typically is acoated plate, placed preferably in a upright holder. Getter agents areincluded inside the inner barrier to provide additional protectionagainst the contaminants.

It is highly desirable that the packaging materials themselves are notinherently prone to potential outgassing acids, vapors and moisture.Preferably, the packaging materials are prepared, i.e., dried ordegassed, so that they are substantially free of potential outgassingacids, vapors, or moisture. Preferably, the barriers are sealed duringpackaging in a dry inert gas atmosphere substantially free of residualacids, amines and moisture.

The inner and outer barriers are formed from a material, such as, ametal foil, a plastic or a filled plastic. The barrier material can be acarbon filled plastic, graphite filled plastic, metal particle or metalfiber filled plastic, organic or inorganic ionic conductor filledplastic, ultraviolet absorber containing plastic, infrared absorbercontaining plastic, or a combination thereof

Preferably, the barrier material for both inner and outer barriers isimpervious to optical radiation, including ultraviolet (UV), deepultraviolet and visible radiation. This barrier material is alsoimpervious to particulates, such as, dust.

Further, the inner and outer barriers are formed from a material whichis impervious to a chemical contaminant. However, the inner barrier canoptionally have one or more openings. Such openings make the innerbarrier pervious to chemical contaminants, including chemicalcontaminants that form outgassing acids, vapors and moisture form thecoated workpiece. These openings in the inner barrier may be covered bya microporous material.

After covering the openings in the inner barrier with a microporousmaterial, the inner barrier will remain pervious to chemicalcontaminants but impervious to particulates. Each of the inner and outerbarriers can be a sealable bag.

Such chemical contaminants typically are solid, liquid or vaporcontaminants capable of causing a reduction in at least one performanceproperty of the coated workpiece. The chemical contaminant comprises anacid precursor or a base precursor. The acid precursor comprises NO₂ andSO₂ emissions and moisture but the chemical contaminant is an acid, abase or moisture.

Depending on its nature, a getter agent can perform a one or more of thefollowing functions: (1) neutralize acidic contaminants; (2) neutralizebasic contaminants; and (3) maintain a desired relative humidity levelwithin the enclosure, for example, of less than 25% at room temperature.

Each of the first and the second getter agents can independently be achemical drying agent, an absorbent for water, an absorbent for a base,an absorbent for an acid, an absorbent for a gas or a combinationthereof Although only one or two types of a getter agents can be used ifthe nature of the contaminant is predictable or known, it is preferablethat a combination of a chemical drying agent, an absorbent for water,an absorbent for a base, an absorbent for an acid and an absorbent for agas are all included in the package to ensure protection against anytype of contaminant that can have a deleterious effect on the resistcoated mask blank. Thus, for example, a preferred getter agent is acombination of silica gel, activated charcoal and potassium carbonatewhich can neutralize the acidic or basic contaminants and also maintainwithin the enclosure the desired relative humidity level.

The getter agents include acidic alumina, basic alumina, acidic silicagel, basic silica gel, activated charcoal, citric acid, potassiumcarbonate, an amine, magnesium sulfate, sodium sulfate, and combinationsthereof Numerous other getter agents know to a person of ordinary skillin the art can also be used. Preferably the getter agent is acombination of silica gel, activated charcoal and potassium carbonatefor neutralizing acidic and/or basic contaminants, absorbing gaseouscontaminats and also for maintaining within the enclosure a relativehumidity level of less than 25% at room temperature.

While inclusion of a getter agent in any of packaged coated workpiece isoptional, the final packaged coated workpiece must have at least onegetter agent within the overall packaged structure.

Referring to FIG. 1, schematic of a packaged, coated workpiece, such as,resist coated mask plates 1 in a sealed enclosure is shown. The sealedenclosure includes a single barrier 6. Preferably, the resist coatedmask plates 1 are disposed in grooves on plate carrier 3, which can be aplate fixture. The sealed enclosure contains a getter agent placed ingetter holding pillows 2 a and 2 b.

The plate carrier 3 has a dummy plate 5, which holds a getter agentlocated in getter holding pillow 2 b. The resist coated mask plates 1,the dummy plate 5 holding getter holding pillow 2 b and the platecarrier 3 may be optionally placed in housing 4. Housing 4 can be asealed enclosure, such as a box, or can be an enclosure having one ormore openings to permit removal of the contaminants by the getter agentin the getter holding pillow 2 a. The resist coated mask plates 1, thedummy plate 5, getter holding pillow 2 b and the plate carrier 3, inhousing 4 (if present), are placed directly in barrier 6 along withgetter holding pillow 2 a so that additional getter capacity is providedby the getter holding pillow 2 a.

The coated workpiece, i.e., the coated plate, can be a single piece orcan be an array of several pieces. They can be placed within the packagein any order, arrangement or configuration. Preferably, the plates areplaced on a carrier, such as, a plate carrier. Alternatively, a fixtureto hold the coated plates in place can be used.

In addition to coated plates, the plate carrier 3 has a dummy plate 5,which holds a getter agent located in getter holding pillow 2 b.Preferably, getter holding pillow 2 b is placed on the dummy plate 5 andsecured by means for holding using, for example, a spring holder. Thespring holder secures the getter pillow 2 b to stay in place on thedummy plate. Preferably, the dummy plate 5 has an opening upon which thegetter holding pillow 2 b is placed and secured so that the getterholding pillow 2 b is in contact with the surrounding atmosphere fromboth sides of the pillow, thereby doubling the effective surface areaexposed to the surrounding atmosphere.

Referring to FIG. 2, schematic of a packaged coated workpiece, such as,resist coated mask plates 11 in a sealed enclosure having multiplebarriers is shown. The sealed enclosure includes an outer barrier 17enclosing getter holding pillow 12 c and inner barrier 16 and itscontents. Both outer barrier 17 and inner barrier 16 are formed from amaterial that is impervious to chemical contaminants. The inner barriercan optionally have one or more openings, which make the inner barrierpervious to chemical contaminants. If the openings in the inner barrier16 are covered using a microporous material, it will still remainpervious to chemical contaminants but impervious to other contaminants.

In this embodiment, the contents of the sealed inner barrier 16 include,as in FIG. 1 above, resist coated mask plates 11, preferably disposed ingrooves on plate carrier 13, which can alternatively be a plate fixture.The sealed inner barrier 16 contains getter agents placed in getterholding pillows 12 a and 12 b. The plate carrier 13 has a dummy plate15, which holds a getter agent located in getter holding pillow 12 b.The resist coated mask plates 11, the dummy plate 15 holding getterholding pillow 12 b and the plate carrier 13 may be optionally placed inhousing 14. Housing 14 can be a sealed enclosure, such as a box, or canbe an enclosure having one or more openings to permit removal of thecontaminants by the getter agent in the getter holding pillow 12 a. Theresist coated mask plates 11, the dummy plate 15, getter holding pillow12 b and the plate carrier 13, in housing 14 (if present), are placeddirectly in inner barrier 16 along with getter holding pillow 12 a sothat additional getter capacity is provided by the getter holding pillow12 a.

Additional getter capacity is provided by the getter holding pillow 12 cbecause of the free flow of vapors and gases through the openings in theinner barrier 16 between the volume defined by the inner barrier and thevolume formed between the inner and outer barriers. As mentioned above,the inner barrier 16 will remain pervious to chemical contaminants evenwhen the openings are covered with a microporous material.

Referring to FIG. 3 a plot of film loss versus wafer aging time foraging of KRS-XE resist coated wafers packaged according to the presentinvention at different temperatures and humidities can be seen. In theabsence of getter agents, film loss after 30 days of storage wassignificant even at low temperatures and humidity, such as, at 20° C.temperature and 44% relative humidity. At higher temperatures andhumidities, film loss after just a few days of storage was dramatic.

Referring to FIGS. 4a, 4 b, 4 c and 4 d, Scanning Electron Micrographs(SEM) of KRS-XE resist coated wafers resolved to 100 nm equal lines andspaces using two doses and after differing degrees of storage can beseen: a) 20 μC/cm² after 50 days storage; b) 21 μC/cm² after 50 daysstorage; c) 20 μC/cm² after 0 days storage (control); and d) 21 μC/cm²after 0 days storage (control).

Referring to FIGS. 5a, 5 b, 5 c and 5 d, Scanning Electron Micrographs(SEM) of KRS-XE resist coated wafers resolved to 75 nm equal lines andspaces using two doses and after differing degrees of storage can beseen: a) 20 μC/cm² after 50 days storage; b) 21 μC/cm² after 50 daysstorage; c) 20 μC/cm² after 0 days storage (control); d) 21 μC/cm² after0 days storage (control).

When FIG. 4a is compared with FIG. 4c, FIG. 4b compared with FIG. 4d,FIG. 5a compared with FIG. 5c and FIG. 5b compared with FIG. 5d, it isclearly seen that the results obtained for the the 50 days stored wafersand the control wafers are the same. The SEM images show that after 50days of storage at ambient temperature and relative humidity, there wasno noticeable reduction or deterioration in sensitivity, performance,image resolution or image quality of the stored resist coated siliconwafers from the controls. The KRS-XE films did not degrade even after 50days of storage in the packaging system of the present invention.

The present invention still further includes a process for preparing apackaged coated workpiece suitable for storage for a period of at leastone week without substantial loss of sensitvity, resolution orperformance. The process comprises the step of sealing a coatedworkpiece and a getter agent in a barrier to enclose the coatedworkpiece and the getter agent to produce the packaged coated workpiece.

In another embodiment, the present invention also includes a process forpreparing a packaged coated workpiece suitable for storage for a periodof at least one week without substantial loss of sensitvity, resolutionor performance. The process includes the steps of: sealing a coatedworkpiece and optionally a first getter agent in an inner barrier toenclose the coated workpiece and the optional first getter agent toproduce a sealed first enclosure; and sealing the sealed first enclosureand optionally a second getter agent in an outer barrier to enclose thesealed first enclosure and the second optional getter agent to producethe packaged coated workpiece, provided that the packaged coatedworkpiece has at least one getter agent.

The sealing is typically carried out using a widely availableheat-saeling device. After placing the coated workpiece in the barriermaterial bag or pouch, the open edge or edges of the bag or pouch areheat-pressed using the heat-saeling device. Preferably, the sealing stepis repeated to obtain two or more seals, therby provide protectionagainst a potential failure of one of the seals.

In still another embodiment, the process can further comprise sealingthe sealed first enclosure and optionally an intermediate getter agentin an intermediate barrier to enclose the sealed first enclosure and theoptional intermediate getter agent to form an intermediate enclosure forenclosure within the outer barrier. The process can further includeforming additional intermediate barriers prior to enclosure within theouter barrier.

The present invention additionally includes a method of increasing thestorage time of a coated workpiece to at least one week withoutsubstantial loss of sensitvity, resolution or performance. The methodcomprises packaging a coated workpiece by a process comprising the stepof sealing a coated workpiece and a getter agent in a barrier to enclosethe coated workpiece and the getter agent to produce the packaged coatedworkpiece.

In yet another embodiment, the present invention includes a method ofincreasing the storage time of a coated workpiece to at least one weekwithout substantial loss of sensitvity, resolution or performance. Themethod comprises packaging a coated workpiece by a process comprising:sealing a coated workpiece and optionally a first getter agent in aninner barrier to enclose the coated workpiece and the optional firstgetter agent to produce a sealed first enclosure; and sealing the sealedfirst enclosure and optionally a second getter agent in an outer barrierto enclose the sealed first enclosure and the optional second getteragent to produce the packaged coated workpiece, with the proviso thatthe packaged coated workpiece has at least one getter agent.

The need to store plates in ambient conditions, which subjects them tomoisture, acids and bases, requires control of the environment.Protection from the outside agents enables economical processing ofphotomasks blanks and insures that the coated resist films have a longshelf life.

The invention is further described in the following examples, which areintended to be illustrative and not limiting.

EXAMPLE 1 (COMPARATIVE)

The sensitivity of coated films is shown for KRS-E (Ketal Resist System)resist coated on silicon wafers. Resist film losses for a 3240 A filmafter storage of the KRS-XE resist coated on silicon wafers at roomtemperature in jar and development in 0.263N tetramethylammoniumhydroxide (TMAH) are shown in the table below.

Control Over process Acetic Over Over Over development Storage acidKOH/K2CO3 Water Ammonia after PEB^(a) Film Loss, 3240A 105A 395A 210A115A 3 days (100%) Film Loss, 155A 798A 279A 15 days Film Loss, 125A1745A 395A 23 days ^(a)PEB: Post Exposure Bake.

EXAMPLE 2 (COMPARATIVE)

KRS-XE coated silicon wafers were exposed to various environmentalconditions and the resulting film loss was measured. Results obtainedafter one week at room temperature are summarized below.

Thickness After Film loss Environmental Original 0.263N after De-Resists Condition Thickness TMAH 60s velopment KRS-XE21 44% Humidity5127 A 5102 A  25 A (K₂CO₃ with water) KRS-XE21 75.7% Humidity 5134 A2492 A 2642 A (NaCl with water) KRS-XE21 Lab Air 5109 A 4862 A  881 A

EXAMPLE 3 (COMPARATIVE) Acid Contamination Studies

KRS-XE resist coated silicon wafers were prepared and the film thicknessof the coating was measured. The coated silicon wafers were placed in anenvironmental test chamber and stored for a predetermined period oftime. After storage for the specified period of time, the coated siliconwafers were immersed in a 0.263N tetramethylammonium hydroxide (TMAH)developer for 60 seconds and the film thickness of the coating wasmeasured again. Film loss after development was measured and recorded.

The amounts of film loss after development are shown in the table below.

Thickness Experi- Original of Film Film Loss mental Storage Film AfterDe- After De- Conditions Time Thickness velopment velopment CommentsAcetic  0 hour 5160 A 5122 A 38 A acid/Water (50/50) Mole ratio Acetic 1 hour 5178 A 3554 A 1624 A acid/Water (50/50) Mole ratio Acetic  2hours 5133 A 4252 A 881 A Film flushed acid/Water with nitrogen (50/50)until no Mole ratio smell of acetic acid Acetic  2 hours 5122 A 4110 A1021 A ½ hr wait acid/Water before (50/50) development Mole ratio Acetic19 hours 5138 A 0^(a) 5138A^(b) acid/Water (50/50) Mole ratio Acetic 19hours 5152 A 0^(a) 5152A^(b) Pumped in acid/Water Vacuum for (50/50) 3hours Mole ratio ^(a)Dissolved in 2-3 seconds ^(b)The entire originalfilm was lost

EXAMPLE 4 (COMPARATIVE) Temperature and Humidity (RH) Chamber Studies

Aging at different temperatures and humidities of KRS-XE resist coatedsilicon wafers in a Relative Humidity Chamber, i.e., in an RH Chamber,in the absence of getter agents was investigated. Plot of film lossversus wafer aging time is shown in FIG. 3. In the absence of getteragents, film loss after 30 days of storage was significant even at lowtemperatures and humidity, such as, at 20° C. temperature and 44%relative humidity. At higher temperatures and humidities, film lossafter just a few days of storage was dramatic.

EXAMPLE 5

A KRS-XE resist coated silicon wafer having a film thickness of 350 nmwas packed according to the present invention in Moisture Barrier Bag®aluminum-metallized polyester having static dissipative polyethylenepackaging material, available from 3M Company, Minneapolis, Minn., inthe presence of a premixed Silica Gel/Charcoal in pillow pack as thegetter agent, available from Donaldson, Inc., Minneapolis, Minn.Potassium carbonate was also included as an additional getter agent in aseparate pillow pack. The packaged resist coated wafer was stored atambient temperature and relative humidity for 50 days. Thereafter, theaged KRS-XE resist coated silicon wafer was exposed patternwise to a 75kV electron beam radiation and then developed in 0.263Ntetramethylammonium hydroxide (TMAH) to produce 100 nm and 75 nm linesand space features. The controls were not stored, i.e., were notsubjected to humidity. They were patternwise exposed to electron beamradiation and developed on the same day. The experimental details andresults obtained are summarized herein below and in FIGS. 4a, 4 b, 4 c,4 d, 5 a, 5 b, 5 c and 5 d.

FIGS. 4a, 4 b, 4 c and 4 d: Scanning Electron Micrographs (SEM) ofKRS-XE resolved to 100 nm equal lines and spaces using two doses andafter differing degrees of storage: a) 20 μC/cm² after 50 days storage;b) 21 μC/cm² after 50 days storage; c) 20 μC/cm² after 0 days storage(control); d) 21 μC/cm² after 0 days storage (control). FIGS. 5a, 5 b, 5c and 5 d: Scanning Electron Micrographs (SEM) of KRS-E resolved to 75nm equal lines and spaces using two doses and after differing degrees ofstorage: a) 20 μC/cm² after 50 days storage; b) 21 μC/cm² after 50 daysstorage; c) 20 μC/cm² after 0 days storage (control); d) 21 μC/cm² after0 days storage (control). FIG. 4a is compared with FIG. 4c; FIG. 4b iscompared with FIG. 4d; FIG. 5a is compared with FIG. 5c; and FIG. 5b iscompared with FIG. 5d. It is clearly seen from the Figures that theresults obtained are the same for the control wafers, which are notstored, and the 50 days stored wafers. The above described SEM imagesshow that the KRS-XE films do not degrade even after 50 days of storagein the above described packaging system. Thus, after 50 days of storageat ambient temperature and relative humidity, there was no noticeablereduction or deterioration in sensitivity, performance, image resolutionor image quality of the stored resist coated silicon wafers whencompared with the resist coated silicon wafer controls, which were notstored.

The present invention has been described with particular reference tothe preferred embodiments. It should be understood that the foregoingdescriptions and examples are only illustrative of the invention.Various alternatives and modifications thereof can be devised by thoseskilled in the art without departing from the spirit and scope of thepresent invention. Accordingly, the present invention is intended toembrace all such alternatives, modifications, and variations that fallwithin the scope of the appended claims.

What is claimed is:
 1. A packaged coated workpiece comprising: aworkpiece coated with a resist film sensitive to optical radiation,particulates or chemical contaminants; a sealed enclosure comprising oneor more barriers for isolating said coated workpiece from an outsideenvironment; and one or more getter agents for producing an enclosuresubstantially free of chemical contaminants; wherein said packagedcoated workpiece is suitable for storage for a period of at least oneweek without substantial loss of sensitvity, resolution or processlatitude.
 2. The packaged coated workpiece of claim 1, wherein saidresist film is a chemically amplified resist or a non-chemicallyamplified resist.
 3. The packaged coated workpiece of claim 2, whereinsaid coated workpiece is a resist-coated mask blank.
 4. The packagedcoated workpiece of claim 3, wherein said coated workpiece is aresist-coated chrome film on a quartz blank.
 5. The packaged coatedworkpiece of claim 1, wherein said workpiece is a substrate suitable formicroelectronic device fabrication.
 6. The packaged coated workpiece ofclaim 1, wherein said workpiece is a substrate suitable for fabricationof a mask selected from the group consisting of an electron beam, x-ray,particle beam, excited state atom beam, ion beam and photo mask.
 7. Thepackaged coated workpiece of claim 1, wherein said sealed enclosurecomprises an inner barrier and an outer barrier.
 8. The packaged coatedworkpiece of claim 7, wherein said inner and outer barriers are formedfrom a material which is impervious to optical radiation andparticulates.
 9. The packaged coated workpiece of claim 8, wherein saidparticulates comprise dust.
 10. The packaged coated workpiece of claim8, wherein said optical radiation is selected from the group consistingof ultraviolet (UV) radiation and visible radiation.
 11. The packagedcoated workpiece of claim 10, wherein said ultraviolet (UV) radiation isa deep ultraviolet radiation.
 12. The packaged coated workpiece of claim7, wherein said inner and outer barriers are formed from a materialwhich is impervious, to a chemical contaminant, with the proviso thatsaid inner barrier optionally has one or more openings for making saidinner barrier pervious to said chemical contaminants.
 13. The packagedcoated workpiece of claim 12, wherein said one or more openings in saidinner barrier optionally are covered by a microporous material therebymaking said one or more covered openings impervious to particulates. 14.The packaged coated workpiece of claim 13, wherein said chemicalcontaminant is a solid, liquid or vapor contaminant capable of causing areduction in at least one performance property of said coated workpiece.15. The packaged coated workpiece of claim 13, wherein said chemicalcontaminant comprises an acid precursor or a base precursor.
 16. Thepackaged coated workpiece of claim 15, wherein said acid precursorcomprises NO₂ and SO₂ emissions and moisture.
 17. The packaged coatedworkpiece of claim 13, wherein said chemical contaminant is an acid or abase.
 18. The packaged coated workpiece of claim 13, wherein saidchemical contaminant is moisture.
 19. The packaged coated workpiece ofclaim 8, wherein said inner and outer barriers are formed from amaterial selected from the group consisting of: a metal foil, a plasticand a filled plastic.
 20. A packaged coated workpiece comprising: aworkpiece coated with a resist film sensitive to optical radiation,particulates or chemical contaminants; a sealed enclosure comprising aninner barrier and outer barrier for isolating said coated workpiece froman outside environment; and at least one getter agent enclosed withinsaid inner barrier and/or said outer barrier for producing an enclosuresubstantially free of chemical contaminants; wherein said packagedcoated workpiece is suitable for storage for a period of at least threemonths without substantial loss of sensitvity, resolution or processlatitude.
 21. A packaged coated workpiece comprising: a workpiece coatedwith a resist film sensitive to optical radiation, particulates orchemical contaminants; an inner barrier sealed to enclose said coatedworkpiece and optionally a first getter agent, to produce a sealed firstenclosure; and an outer barrier sealed to enclose said sealed firstenclosure and optionally a second getter agent, to produce a packagedcoated workpiece suitable for storage for a period of at least one weekwithout substantial loss of sensitvity, resolution or performance, withthe proviso that said packaged coated workpiece has at least one getteragent.
 22. The packaged coated workpiece of claim 21, wherein saidresist film is a chemically amplified resist or a non-chemicallyamplified resist.
 23. The packaged coated workpiece of claim 22, whereinsaid coated workpiece is a resist-coated mask blank.
 24. The packagedcoated workpiece of claim 23, wherein said coated workpiece is aresist-coated chrome film on a quartz blank.
 25. The packaged coatedworkpiece of claim 21, wherein said workpiece is a substrate suitablefor microelectronic device fabrication.
 26. The packaged coatedworkpiece of claim 21, wherein said workpiece is a substrate suitablefor fabrication of a mask selected from the group consisting of anelectron beam, x-ray, particle beam, excited state atom beam, ion beamand photo mask.
 27. The packaged coated workpiece of claim 21, whereinsaid inner and outer barriers are formed from a material which isimpervious to optical radiation and particulates.
 28. The packagedcoated workpiece of claim 27, wherein said particulates comprise dust.29. The packaged coated workpiece of claim 27, wherein said opticalradiation is selected from the group consisting of: ultraviolet (UV)radiation and visible radiation.
 30. The packaged coated workpiece ofclaim 29, wherein said ultraviolet (UV) radiation is a deep ultravioletradiation.
 31. The packaged coated workpiece of claim 21, wherein saidinner and outer barriers are formed from a material which is impervious,to a chemical contaminant, with the proviso that said inner barrieroptionally has one or more openings for making said inner barrierpervious to said chemical contaminants.
 32. The packaged coatedworkpiece of claim 31, wherein said one or more openings in said innerbarrier optionally are covered by a microporous material thereby makingsaid one or more covered openings impervious to particulates.
 33. Thepackaged coated workpiece of claim 32, wherein said chemical contaminantis a solid, liquid or vapor contaminant capable of causing a reductionin at least one performance property of said coated workpiece.
 34. Thepackaged coated workpiece of claim 32, wherein said chemical contaminantcomprises an acid precursor or a base precursor.
 35. The packaged coatedworkpiece of claim 34, wherein said acid precursor comprises NO₂ and SO₂emissions and moisture.
 36. The packaged coated workpiece of claim 32,wherein said chemical contaminant is an acid or a base.
 37. The packagedcoated workpiece of claim 32, wherein said chemical contaminant ismoisture.
 38. The packaged coated workpiece of claim 21, wherein each ofsaid first and said second getter agents is capable of maintainingwithin said enclosures a relative humidity level of less than 25% atroom temperature.
 39. The packaged coated workpiece of claim 38, whereineach of said first and said second getter agents is independentlyselected from the group consisting of: a chemical drying agent, anabsorbent for water, an absorbent for a base, an absorbent for an acid,an absobent for a gas and a combination thereof.
 40. The packaged coatedworkpiece of claim 39, wherein each of said first and said second getteragents is independently selected from the group consisting of alumina,silica gel, activated charcoal, citric acid, potassium carbonate, anamine and a combination thereof.
 41. The packaged coated workpiece ofclaim 40, wherein each of said first and said second getter agents is acombination of silica gel, activated charcoal and potassium carbonate.42. The packaged coated workpiece of claim 21, wherein at least some ofsaid first or said second getter agent is enclosed in a microporousmaterial.
 43. The packaged coated workpiece of claim 21, wherein saidmicroporous material is a fluorinated hydrocarbon material.
 44. Thepackaged coated workpiece of claim 43, wherein said fluorinatedhydrocarbon material is selected from the group consisting of: afluorocarbon, vinylidene fluoride homopolymer, vinylidene fluoridecopolymer, Goretex™, Teflon™ and a combination thereof.
 45. The packagedcoated workpiece of claim 21, wherein said said inner and outer barriersare formed from a material selected from the group consisting of a metalfoil, a plastic and a filled plastic.
 46. The packaged coated workpieceof claim 45, wherein said said material is selected from the groupconsisting of: a carbon filled plastic, grafite filled plastic, metalparticle, metal platelet or metal fibre filled plastic, organic orinorganic ionic conductor filled plastic, ultraviolet absorbercontaining plastic, infrared absorber containing plastic, and acombination thereof.
 47. The packaged coated workpiece of claim 21,wherein each of said inner barrier and said outer barrier is a sealablebag.
 48. The packaged coated workpiece of claim 21, further comprisingbetween said inner barrier and said outer barrier, an intermediatebarrier sealed to enclose said sealed first enclosure and optionally anintermediate getter agent, to produce a sealed intermediate enclosure.49. The packaged coated workpiece of claim 48, further comprisingadditional intermediate barriers.